Traditional shoe lasts have been widely used as both a model and a form to construct mass-produced shoes designed to fit a broad range of the feet of a given population. These traditional shoe lasts have mimicked a universal human foot based on generalized length, width, and girth measurements of the foot.
Traditional lasts are typically produced by constructing a model last for a particular shoe style, for example a women's 6B for a dress shoe. Last makers then grade shoe lasts between sizes in lengths and widths starting from this model last utilizing accepted grading systems. Well-known last grading systems include: arithmetic; geometric; and proportional. These grading systems utilize proportional or standardized measurements at various grading points to. move between length sizes and width sizes in a particular style of shoe last. Texts such as Karl C. Adrian, American Last Making (1991) explain some generally accepted grading points and measurements for length, width, and girth for shoe lasts. For example, generally accepted measurements are utilized for the length of the bottom of the last measured utilizing a last stick for a particular shoe style and size. Generally accepted girth measurements, including the instep girth, waist girth, and ball girth measurements, are also used for a traditional shoe last for a particular shoe style and category of wearer such as men, women, and children.
Although these lasts are used to manufacture mass-produced shoes to fit a "universal" foot, it is well known that configurations of human feet vary greatly from person to person and among different populations of the world. Mass-produced shoes made on traditional lasts fit poorly on many feet causing or contributing to various foot problems and discomfort. It has been recognized that many problems of comfort, wear and tear, and foot ulcerations are associated with walking, standing, or running in shoes.
Various approaches have been made in mass-produced shoe design and last design to increase comfort and reduce associated foot problems. One approach has been to incorporate extra support or cushioning in the innersole, shoe upper, midsole, and outer sole. Shoes have also been developed which have attempted to emulate the sole of the foot of the wearer to thereby provide a degree of comfort when walking, running or the like. The design of these shoes typically anticipated the wearer to use a conventional thin sock with the shoe so that the shoe innersole of the shoe substantially corresponds in size to the sole of the foot. Examples of such shoes may be seen in U.S. Pat. No. 4,831,750 by Muller entitled "Shoe-Construction, Shoe Construction Product, and Method of Fabricating the Products" and U.S. Pat. No. 4,305,212 by Coomer entitled "Orthotically Dynamic Footwear."
Last designs have also been modified to produce shoes which conform to various portions of the foot or allow for foot deformities or irregularities. See for example, U.S. Pat. No. 3,991,430 by Gumbs entitled "Shoe Last," U.S. Pat. No. 1,756,587 by Durkee entitled "Last," U.S. Pat. No. 2,044,676 by Finkany entitled "Shoe Last," and U.S. Pat. No. 106,030 by Burke entitled, "Boot or Shoe." Lasts have also been adapted to construct shoes with additional components such as steel toe plates for safety shoes as seen in U.S. Pat. No. 2,737,671 by Hill entitled "Last for Safety Shoes" and U.S. Pat. No. 2,498,037 by W. G. Greenan entitled "Last for Use in the Manufacture of Safety Shoes."
Sock manufacturers, including the common assignee for the present invention, have modified sock designs to increase the comfort and reduce stress on the feet when wearing shoes. For instance, the common assignee recognized that when wearing shoes, the major wear and tear on the foot occurs in the ball and heel regions of the foot because a major portion of the person's weight is distributed in these regions when standing, walking, or running. As a result of this recognition, Thorneburg, the common assignee, developed the sock disclosed in U.S. Pat. No. 4,194,249 entitled Jogging and Running Athletic Sock (hereinafter "the Thorneburg '249 patent") which is incorporated herein by reference. The sock seen in the Thorneburg '249 patent is a custom-shaped knit sock having an increased density of fabric in the ball and heel portions of the sock to provide added comfort to the wearer and to reduce the damage to these regions of the foot. Another custom-shaped sock may be seen in U.S. Pat. No. 5,335,517 to Throneburg et al. entitled Anatomical Isotonic Sock and Method of Knitting the Same (hereinafter "the Throneburg '517 patent") and incorporated by reference herein. The sock illustrated in the Throneburg '517 patent has varying terry loop density in the foot portion of the sock so as to provide a therapeutic and preventative benefit to the foot of the wearer.
Traditional lasts provide insufficient girth or volume, width, or length to produce a shoe which can accommodate a custom-shaped sock when positioned on the foot of a wearer and do not properly fit. Therefore, the therapeutic and comfort benefits of custom-shaped socks are reduced or eliminated by the poor fit of shoes constructed on a traditional last when positioned on the foot of a wearer of a custom-shaped sock.
Alternatively, a wearer may attempt to obtain a more comfortable fit by choosing a larger size of a shoe constructed with a traditional last. The result of wearing a larger shoe will be a poor fit because the relationship of the portions of the foot will not correspond to the elements of the shoe. For instance, the arch or the foot will be out of alignment or proportion with the arch portion of the innersole. Consequently, individuals attempting to obtain the benefits of a comfortable and cushioned fit must choose between not wearing a custom-shaped sock or wearing the custom-shaped sock in a shoe that is too large.